In general, there are cases when a salicide region is formed selectively for meeting a signal speed of a semiconductor device product. Particularly, there are semiconductor devices that require salicide, not on an active region, but only on a gate of a transistor.
FIGS. 1A and 1B illustrate sections for explaining occurrence of over etch at a non-salicide region (active region), and a salicide region when an oxide film is etched selectively for fabricating a semiconductor device with salicide according to a related art method.
Referring to FIG. 1A, in a related art method for fabricating a semiconductor device, a shallow trench isolation (STI) film 204 is formed on a substrate 202, and deposition and etching are repeated selectively, to form a gate oxide film 206, a gate electrode 208, and spacers 210 are formed on predetermined positions of the substrate 202, respectively. In this instance, though not shown on the drawing, ions are injected after formation of the gate electrode 208, to form source/drain electrodes in the substrate in predetermined regions thereof.
Next, an oxide film 212 of a thickness is deposited on an entire surface of the substrate 202, a photomask process (PR coating, exposure, and development) is performed, to form an etch mask 214 having a pattern defining a salicide region thereon. In FIG. 1A, reference symbol A1 denotes a non-salicide region (active region), and reference symbol A2 denotes a salicide region.
Then, as shown in FIG. 1B, wet etching is performed with a solution containing HF or the like, to remove, for an example, the oxide film 212 on the salicide region A2 selectively, and expose the salicide region A2, to form a non-salicide region of an oxide film.
However, the related art method, in which the non-salicide region is formed by the wet etching with a solution containing HF after defining a salicide region with an etch mask, i.e., wet etching having isotropic etching characteristics, causes fast etching at an interface of films, to cause, for an example, as shown at a reference symbol B1 in FIG. 1B, over-etching up to the active region (i.e., the etching encroaches into the active region to form salicide), and, as shown at a reference symbol B2 in FIG. 1B, lateral etching even at the gate electrode, all of which result in poor electric characteristics of the semiconductor device at the end, to drop productivity and reliability of the product.